How to define PROMO CODES

I got two promo codes, but cannot find out where to define, what they are for. How long are they good for? What do they get the user? When do they expire? Where can I set the limits and define what the promo code is good for?

Cannot find a video or even a readable page telling me WHERE to click.

Help!

How to define PROMO CODES
 
 
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